1. Field of the Invention
The present invention generally relates to compositions, methods for forming compositions, and methods of using compositions for hormonally reducing tadpole shrimp populations. More specifically, embodiments of the present invention relate to processes, methods, and compositions for organically inhibiting tadpole shrimp reproduction to prevent damage to agricultural crops, including rice.
2. Background and Description of Related Art
Triops longicaudatus, commonly known as the tadpole shrimp, is a small pest which inhabits temporary pools. Adult tadpole shrimp will deposit eggs in the bed of such pools, and the eggs eventually become cysts which are highly resistant to harsh physical conditions (such as, for example, dehydration and extreme temperatures). These cysts have the ability to remain viable in a dormant state for several years in dry, unflooded soil. Upon the flooding of the soil with water, many cysts will activate and begin to hatch.
The rapid growth and reproduction of tadpole shrimp have created a persistent problem in infested rice fields which are typically flooded prior to the planting of the rice crop. In general, tadpole shrimp hatch within two or three days after the cysts are exposed to a sufficient amount with water. Upon hatching, the tadpole shrimp begin to forage for organic material to feed on. The foraging behavior, including digging and agitating the soil, often dislodges or prevents young rice cotyledons from rooting in the ground. This disruption can create yield losses amounting to 20% or greater for affected rice fields. Although tadpole shrimp foraging behavior can disrupt the rice seedlings in the process of rooting, once the roots are well established in the soil, the tadpole shrimp pose minimal, if any, threat of harm or injury to the rice plant and resulting crop yields.
Because the tadpole shrimp has become highly adaptable to survive through extreme environmental conditions, there is no simple way to eliminate them from the environment. Tadpole shrimp eggs and cysts have proven to survive in a desiccated state for a number of years. Additionally, not all tadpole shrimp eggs hatch the first time the given area is flooded, but may instead hatch during a subsequent flooding of the area. Further, the eggs are easily spread by modern farming techniques, making containment of the tadpole shrimp to certain areas very difficult. Elimination of tadpole shrimp is also exacerbated by their high reproductive fecundity; tadpole shrimps can begin developing oocytes in as little as four days, and are further capable of producing hundreds of eggs.
Conventional attempts at controlling tadpole shrimp population include the application of copper sulfate. However the use of copper sulfate is not considered to be environmentally sustainable, and its use is becoming disfavored. The United States Environmental Protection Agency has categorized copper sulfate as a class I hazardous toxin, and its use may be prohibited in the near future. Moreover, the presence of copper sulfate residue in the soil is unfavorable to rice growing conditions.
Recent scientific studies have shown that the hormone methyl farnesoate [methyl-(2E,6E,10E)-3,7,11-trimethyldodecatri-2,6,10-eneoate] (sometimes referred to herein as “MF”) inhibits growth, development, and gamete production in some pests, such as tadpole shrimp. Studies have shown that methyl farnesoate reduces sexual development of tadpole shrimp. Methyl farnesoate is easily oxidized into farnesoic acid and concentrations of methyl farnesoate rapidly decrease when exposed to oxidizing agents in the environment. Because methyl farnesoate oxidizes quickly and therefore will not build up large concentrations in the soil, and because it is a fatty acid, it is not considered to be harmful to the environment or adversely affect crop production. However, it is for these same reasons that administration of methyl farnesoate is difficult to administer.
U.S. Pat. No. 5,161,481 concerns using methyl farnesoate to increase larval production in white shrimp, or Litopenaeus (as Penaeus) vannamei, in marine environments. The white shrimp of the '481 patent belong to the Class: Malacostraca, Subclass: Eumalacostraca, Superorder: Eucarida, Order: Decepoda, Suborder: Dendrobranchiata, Superfamily: Penaeoidea, and Family: Penaeidae, which are marine shrimp. In contrast, the tadpole shrimp referred to in the present application belong to the Class: Branchiopoda, Subclass: Phyllopoda, and Order: Notostaca, which are fresh water organisms. The different biological characteristics are believed to explain why the same or similar compounds, and particularly methyl farnesoate, produce different reproductive effects on these different organisms.
It is therefore desirable to provide economical and environmentally friendly compositions and methods for preventing crop loss due to tadpole shrimp population without the use of copper sulfate.